I sit firmly in the Sena camp. I like her naiveté, her tearful dashes out the door and down the hallway, and shy pleas for help getting caught up to the rest of the world. In spite of her physical appearance and casual attire, she's quite reserved.
She, Yozora, and Kodaka really came off pathetic this episode. Kodaka was okay, because he clearly had a cell to use to contact his family members, even if he didn't use it enough that he had to go looking for it. Sena at least didn't have one at all, she had a landline that she knew how to use, but obviously didn't utilize it that often. Yozora was the most pathetic. Yozora had a cellphone in the hope that she would one day be able to put friends into it, she didn't even have any family in it.
Sena is just somehow completely isolated from the normal world, despite always being followed by boys and being popular and fashionable. It's somewhat endearing that she's so shy in the face of Kodaka, who she deems to be a little more connected and up to date. She should obviously be talking to Rika and Yukimura. Despite their blatant quirks, they came off pretty normal this episode.
I am liking that Yozora's pranks are starting to backfire on her. She's trying to drive Sena off and get some enjoyment out of it, but since he taught her how to swim, Sena has started to flee to Kodaka. Sena is depending on him, like a friend would. Now Yozora ends up being the one left out, no matter how much she tries to ditch Sena from club activities. It's all part of Yozora's tomboy nature, but she's has to learn sometime.